## Energies for interactions

Ayesha Aslam-Mir 3C
Posts: 115
Joined: Wed Sep 30, 2020 9:43 pm

### Energies for interactions

When reviewing interactoins between ion-ion and ion-dipole interactions, where do the energies come from? I understand that, in an ion-ion example, the two are attracted to each other, but I don't undersatnd how that contributes to the negative energy (being released)?

SamayaJoshi1A
Posts: 103
Joined: Wed Sep 30, 2020 9:37 pm

### Re: Energies for interactions

I don't understand this either! And could someone explain the main differences between these two types of forces? Thanks.

JoshMoore2B
Posts: 90
Joined: Wed Sep 30, 2020 9:51 pm

### Re: Energies for interactions

Ayesha Aslam-Mir 2E wrote:When reviewing interactoins between ion-ion and ion-dipole interactions, where do the energies come from? I understand that, in an ion-ion example, the two are attracted to each other, but I don't undersatnd how that contributes to the negative energy (being released)?

It is better not to think of the interactions as energy being released, but instead the amount of energy required to break the bond. If you viewed the interaction from the perspective of the ions, then you would say your system is the ion-ion interaction. To break the ion-ion interaction, energy must be added to your system, similar to how it takes energy, say, tear a piece of paper. So, if it takes an input of energy (a + value) to break the interaction (which would return the ions to state where they aren't interacting, which has 0 energy), then the interaction must have - energy, since the only way to get 0 from adding is if your system was at a negative value beforehand.

Say an ion-ion interaction was as follows:

When interacting, the system had X energy.

After energy is added (a positive number), the system had 0 energy.

Therefore, you have X + a positive number = 0, meaning X must be a negative number.

I hope this makes some sense. The main idea is that the energy is denoted as negative because positive energy must be input to return the system back to 0.

Ayesha Aslam-Mir 3C
Posts: 115
Joined: Wed Sep 30, 2020 9:43 pm

### Re: Energies for interactions

JoshMoore3D wrote:
Ayesha Aslam-Mir 2E wrote:When reviewing interactoins between ion-ion and ion-dipole interactions, where do the energies come from? I understand that, in an ion-ion example, the two are attracted to each other, but I don't undersatnd how that contributes to the negative energy (being released)?

It is better not to think of the interactions as energy being released, but instead the amount of energy required to break the bond. If you viewed the interaction from the perspective of the ions, then you would say your system is the ion-ion interaction. To break the ion-ion interaction, energy must be added to your system, similar to how it takes energy, say, tear a piece of paper. So, if it takes an input of energy (a + value) to break the interaction (which would return the ions to state where they aren't interacting, which has 0 energy), then the interaction must have - energy, since the only way to get 0 from adding is if your system was at a negative value beforehand.

Say an ion-ion interaction was as follows:

When interacting, the system had X energy.

After energy is added (a positive number), the system had 0 energy.

Therefore, you have X + a positive number = 0, meaning X must be a negative number.

I hope this makes some sense. The main idea is that the energy is denoted as negative because positive energy must be input to return the system back to 0.

Oh, I see in a sense. So the ion-ion interactions shwon required more energy to break their bond, while dipole induced-dipoles have smaller energies requird because they are weak forces. (hopefully that is true haha)

Thank you for explaining the negative value as well; it was well-explained!

Alex Benson
Posts: 75
Joined: Wed Sep 30, 2020 9:44 pm

### Re: Energies for interactions

Hi! I think of the energies as the energy that would be required to break the bond. In the ion-ion example I believe that it has a negative energy because it requires energy to break the bond, however more energy is released from the bond thereafter, which is why the bond has negative energy.